1. Field
Exemplary embodiments relate to an energy storage device such as an ultracapacitor or battery, and more particularly, to a terminal connecting device for connecting a plurality of cells for a high voltage energy storage assembly.
2. Description of the Related Art
Generally, a representative example of an electrical energy storage device includes a battery and a capacitor.
Among capacitors, an ultracapacitor, also known as a supercapacitor, is an energy storage device having characteristics in between those of an electrolytic condenser and a secondary battery. Since an ultracapacitor has high efficiency and a semipermanent life span, the ultracapacitor is considered as a next-generation energy storage device that is useable in parallel with or in replace of a secondary battery.
To implement a high voltage battery using an ultracapacitor, a high voltage module of several hundred volts V is needed. The high voltage module is a high voltage ultracapacitor assembly in which a necessary number of ultracapacitors as unit cells are connected. In this instance, a busbar is used in connecting a plurality of ultracapacitors.
FIGS. 1A to 1C illustrate an energy storage module or assembly in which cell terminals are connected by an interference fit using a conventional busbar.
Conventionally, a plurality of cells 10 are connected using a busbar 20 to form a module or assembly with the busbar 20 interference-fitted into cell terminals 11 of the cells 10, as shown in FIGS. 1A to 1C.
In other words, the busbar 20 having holes corresponding to the cell terminals 11 is prepared and then placed such that the holes are aligned with the corresponding cell terminals 11. Next, the busbar 20 is forcedly inserted and press-fitted into the cell terminals 11.
However, this connection by an interference fit using the conventional busbar 20 has advantages such as being simple in configuration, inexpensive costs, and easy to assemble, but cannot guarantee the connection reliability when the tightness of fit decreases. That is, the vibration resistance or durability is low.
Moreover, when the fit becomes loose or the cell terminal 11 slips off, it will have a bad influence on a system using the module or assembly.
Also, to apply an interference fit, the precision of the busbar 20 and the cell terminals 11 to be fitted is very important. This is because it could lead to the possibility of fault occurrence increasing along with the difficulty in manufacturing the components.
FIGS. 2A to 2D illustrate an energy storage module or assembly in which cell terminals are connected with nuts using a conventional busbar.
As shown in FIGS. 2A to 2D, the busbar 20 is tightly coupled to the cell terminals 11 with nuts 30 that improve the coupling strength between the busbar 20 and the cell terminals 11.
In other words, the cell terminals 11 protrude from the top of the cells 10 and the busbar 20 has holes corresponding to the cell terminals 11. The busbar 20 is placed such that the holes are aligned with the corresponding cell terminals 11. Next, the busbar 20 is secured to the cell terminals 11 with the nuts 30.
This conventional connection using the nuts 30 improves the coupling strength or connection reliability, but increases the full size of the module or assembly due to the height and volume of the nuts 30 used.
Because of the problems above, this conventional connection does not go with the trend of equipments using an energy storage module or assembly toward minimization and light weight, and unnecessary height and volume has a bad influence on the design of the products. That is, the freedom of the design reduces and the design of the products is restricted.